mailbox: bcm-flexrm-mailbox: Fix FlexRM ring flush timeout issue

RING_CONTROL reg was not written due to wrong address, hence all
the subsequent ring flush was timing out.

Fixes: a371c10e ("mailbox: bcm-flexrm-mailbox: Fix FlexRM ring flush sequence")
Signed-off-by: NRayagonda Kokatanur <rayagonda.kokatanur@broadcom.com>
Signed-off-by: NRay Jui <ray.jui@broadcom.com>
Reviewed-by: NScott Branden <scott.branden@broadcom.com>
Signed-off-by: NJassi Brar <jaswinder.singh@linaro.org>

drivers/mailbox/bcm-flexrm-mailbox.c

@@ -1396,9 +1396,9 @@ static void flexrm_shutdown(struct mbox_chan *chan)
 
 	/* Clear ring flush state */
 	timeout = 1000; /* timeout of 1s */
-	writel_relaxed(0x0, ring + RING_CONTROL);
+	writel_relaxed(0x0, ring->regs + RING_CONTROL);
 	do {
-		if (!(readl_relaxed(ring + RING_FLUSH_DONE) &
+		if (!(readl_relaxed(ring->regs + RING_FLUSH_DONE) &
 		      FLUSH_DONE_MASK))
 			break;
 		mdelay(1);